U.S. patent number 7,938,224 [Application Number 12/528,007] was granted by the patent office on 2011-05-10 for coating for acoustic treatment integrating the function of frost treatment with hot air.
This patent grant is currently assigned to Airbus Operations SAS. Invention is credited to Bernard Duprieu, Valerie Frustie, Fabrice Gantie.
United States Patent |
7,938,224 |
Frustie , et al. |
May 10, 2011 |
Coating for acoustic treatment integrating the function of frost
treatment with hot air
Abstract
A coating for acoustic treatment relative to an aircraft's
surface, in particular a leading edge such as an air intake of an
aircraft nacelle, includes an acoustically resistive layer, at
least one alveolar structure (30), and a reflective layer. The
alveolar structure (30) includes a number of tubes that empty out,
on the one hand, at a first imaginary surface (34), and, on the
other hand, at a second imaginary surface (36). The alveolar
structure (30) includes cut-outs or openings (38) made at the side
walls of certain tubes that make it possible to link adjacent tubes
so as to create a network of communicating tubes that isolate at
least one tube or a group of non-communicating tubes, whereby at
least one of the communicating tubes is connected to at least one
hot gas intake (40).
Inventors: |
Frustie; Valerie (Toulouse,
FR), Duprieu; Bernard (Toulouse, FR),
Gantie; Fabrice (Toulouse, FR) |
Assignee: |
Airbus Operations SAS
(Toulouse, FR)
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Family
ID: |
38477324 |
Appl.
No.: |
12/528,007 |
Filed: |
February 14, 2008 |
PCT
Filed: |
February 14, 2008 |
PCT No.: |
PCT/FR2008/050244 |
371(c)(1),(2),(4) Date: |
August 20, 2009 |
PCT
Pub. No.: |
WO2008/104714 |
PCT
Pub. Date: |
September 04, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100096213 A1 |
Apr 22, 2010 |
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Foreign Application Priority Data
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Feb 20, 2007 [FR] |
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07 53358 |
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Current U.S.
Class: |
181/214; 181/290;
181/292; 181/213 |
Current CPC
Class: |
F02C
7/047 (20130101); B64D 33/02 (20130101); F02C
7/045 (20130101); B64D 2033/0206 (20130101); B64D
2033/0286 (20130101); F05D 2260/96 (20130101); F05D
2250/283 (20130101) |
Current International
Class: |
B64D
33/02 (20060101) |
Field of
Search: |
;181/290,292,214,213
;244/1N ;415/119 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 103 462 |
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May 2001 |
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EP |
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1 232 944 |
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Aug 2002 |
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EP |
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1 495 963 |
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Jan 2005 |
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EP |
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2 887 518 |
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Dec 2006 |
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FR |
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Other References
International Search Report dated Sep. 29, 2008, from corresponding
PCT application. cited by other.
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Primary Examiner: Enad; Elvin G
Assistant Examiner: Phillips; Forrest M
Attorney, Agent or Firm: Young & Thompson
Claims
The invention claimed is:
1. Coating for acoustic treatment relative to an aircraft's
surface, said coating comprises: an acoustically resistive layer
(28), at least one alveolar structure (30), and a reflective layer
(32), wherein, said alveolar structure (30) comprises a number of
tubes that empty out, on the one hand, at a first imaginary surface
(34), and, on the other hand, at a second imaginary surface (36),
and said alveolar structure (30) further comprises i) sets of one
or more tubes with side walls free of cut-outs and openings, and
ii) tubes with side walls having cut-outs (38) linking adjacent
tubes so as to create a network of communicating tubes for
communicating hot gas around one of the sets of one or more tubes
with side walls free of cut-outs and openings, wherein at least one
of the communicating tubes is connected to at least one hot gas
intake (40).
2. Coating for acoustic treatment according to claim 1, wherein the
alveolar structure (30) comprises a series of first non-secant
bands (48) that are spaced apart, and at least one second series of
second non-secant bands (50) that are spaced apart, and wherein the
first bands (48) are secant with the second bands (50) so as to
delimit a tube between, on the one hand, two first adjacent bands
(48), and, on the other hand, two second adjacent bands (50).
3. Coating for acoustic treatment according to claim 2, arranged at
an air intake of an aircraft nacelle, wherein the first bands
called longitudinal bands are arranged in radial planes that
contain the longitudinal axis (18) of the nacelle.
4. Coating for acoustic treatment according to claim 2, wherein
each second band (50) called a transverse band is essentially
perpendicular to the tangent at the second imaginary surface
(36).
5. Coating for acoustic treatment according to claim 3, wherein
each longitudinal band (48) is essentially perpendicular to the
tangent of each transverse band (50).
6. Coating for acoustic treatment according to claim 2, wherein the
longitudinal bands (48) comprise first cut-outs (52) that work with
second cut-outs (54) that are provided at the transverse bands
(50).
7. Coating for acoustic treatment according to claim 2, wherein it
comprises, on the one hand, first cells (66) that are dedicated to
the channeling of hot air for the treatment of frost with small
cross-sections, delimited by bands (48, 50) that are brought close
together, and second cells (68) that are dedicated to acoustic
treatment with larger cross-sections, delimited by bands (48, 50)
with a larger spacing than that of the bands (48, 50) that delimit
the first cells.
8. Coating for acoustic treatment according to claim 1, wherein it
comprises a cavity or a channel (70), connected to a hot gas intake
(40), arranged at a portion of the periphery of the alveolar
structure, able to communicate with at least one cell (68) that is
dedicated to the channeling of the hot gas.
9. Leading edge of an aircraft that incorporates a coating for
acoustic treatment according to claim 1.
10. Air intake of a nacelle of an aircraft that incorporates a
coating for acoustic treatment according to claim 1.
11. Coating for acoustic treatment according to claim 3, wherein
each second band (50) called a transverse band is essentially
perpendicular to the tangent at the second imaginary surface
(36).
12. Coating for acoustic treatment according to claim 4, wherein
each longitudinal band (48) is essentially perpendicular to the
tangent of each transverse band (50).
13. Coating for acoustic treatment according to claim 11, wherein
each longitudinal band (48) is essentially perpendicular to the
tangent of each transverse band (50).
14. Coating for acoustic treatment according to claim 3, wherein
the longitudinal bands (48) comprise first cut-outs (52) that work
with second cut-outs (54) that are provided at the transverse bands
(50).
15. Coating for acoustic treatment according to claim 3, wherein it
comprises, on the one hand, first cells (66) that are dedicated to
the channeling of hot air for the treatment of frost with small
cross-sections, delimited by bands (48, 50) that are brought close
together, and second cells (68) that are dedicated to acoustic
treatment with larger cross-sections, delimited by bands (48, 50)
with a larger spacing than that of the bands (48, 50) that delimit
the first cells.
16. Coating for acoustic treatment relative to an aircraft's
surface, said coating comprises: an acoustically resistive layer
(28); a reflective layer (32); and an alveolar structure (30)
delimited by a first imaginary surface (34) and by a second
imaginary surface (36), the reflective layer (32) being connected
to the alveolar structure at the first imaginary surface (34) and
the acoustically resistive layer (28) being alveolar structure at
the at the second imaginary surface (36), the alveolar structure
(30) comprised of tubes that empty out at the first imaginary
surface and at the second imaginary surface, said tubes sealed by,
on the one hand, the acoustically resistive porous layer, and, on
the other hand, the reflective layer, so as to form cells, the
alveolar structure (30) further comprised of cut outs (38),
wherein, a first set of said tubes has side walls free of said
cut-outs, the first set of said tubes defining non-communicating
cells isolated from one another and having an acoustic function, a
second set of said tubes has side walls with said cut-outs (38),
the cut-outs link adjacent tubes of said second set of tubes so as
to create a network of communicating tubes for communicating hot
gas around one or more tubes of the first set of said tubes with
side walls free of cut-outs, and at least one tube of said first
set of said tubes of the network of communicating tubes has a hot
gas intake (40).
Description
This invention relates to a coating for acoustic treatment
integrating the function of frost treatment with hot air, whereby
said coating is designed in particular for a leading edge of an
aircraft, and more particularly for an air intake of an aircraft
nacelle.
To limit the impact of the sound pollution close to airports, the
international standards are increasingly restrictive as far as
sound emissions are concerned.
Techniques have been developed for reducing the noise that is
emitted by an aircraft, in particular by arranging, at walls of the
tubes of nacelles, coatings that are designed to absorb a portion
of the sound energy, in particular by using the principle of
Helmholtz resonators. In a known manner, this acoustic treatment
comprises--from the outside to the inside--an acoustically
resistive porous layer, an alveolar structure, and a reflective
layer that is impermeable to sound waves so that the coating is
effective.
For the moment, because of the different stresses, for example
shaping or compatibility with other equipment, the extent of the
treated surfaces is limited. Thus, the coating is not very
compatible with the systems that make it possible to prevent the
formation and/or the accumulation of ice and/or frost that are
necessary in these zones.
These systems are divided into two large families, the first family
called defrosting systems that make it possible to limit the
formation of ice and/or frost, and the second family called
de-icing systems that limit the accumulation of ice and/or frost
and act once the ice and/or frost is formed. Hereinafter, a frost
treatment system or process is defined as a defrosting system or
process or a de-icing system or process.
This invention relates more particularly to a frost treatment
process that consists in using hot air that is taken from the
engine and fed back at the inside wall of the leading edges. This
high-quality system is not very compatible with the acoustic
treatment coating to the extent that the latter is relatively thick
and consists of cells that contain air and that act as an
insulating material.
To attempt to make the acoustic and frost treatments compatible, a
solution that is described in the documents EP-1,103,462 and U.S.
Pat. No. 5,841,079 provides holes in the reflective wall so that
the hot air penetrates the cells of the acoustic coating.
This solution, however, is not satisfactory for the following
reasons:
The cells of the alveolar structure that comprise one or more holes
at the reflective layer are less capable in terms of acoustic
treatment, whereby the waves dissipate less well in said cells. To
reduce this alteration, a solution consists in reducing the
cross-section of the holes. In this case, the volume of air at a
constant flow rate is reduced, making the de-icing less effective.
Furthermore, these holes of reduced cross-sections can be plugged
more easily, which eliminates the de-icing function in the
corresponding zone.
According to another problem, to the extent that the alveolar
structure that consists of a honeycomb is deformed during its
installation, certain holes of the reflective layer can be arranged
facing a side wall that delimits two cells. In this case, the
operation in terms of acoustic treatment of two cells is altered,
and the de-icing function is also altered, whereby the hole is
partially plugged by the wall.
Finally, according to another problem, since a pressure balance
forms inside the rim of the air intake, it is not possible to
isolate certain portions of the rim so as to blow in there a
stronger de-icing air pressure, in particular at the spots where
the frost is deposited in larger quantities.
The purpose of this invention is to overcome the drawbacks of the
prior art by proposing a coating that makes acoustic treatment and
frost treatment with a hot gas compatible, whereby said coating is
designed in particular for a leading edge and more particularly a
nacelle air intake.
For this purpose, the invention has as its object a coating for
acoustic treatment relative to a surface of an aircraft, in
particular at a leading edge such as an air intake of an aircraft
nacelle, whereby said coating comprises an acoustically resistive
layer, at least one alveolar structure, and a reflective layer,
whereby said alveolar structure comprises a number of tubes that
empty out, on the one hand, at a first imaginary surface, and, on
the other hand, at a second imaginary surface, characterized in
that the alveolar structure comprises cut-outs or openings made at
the side walls of certain tubes that make it possible to link
adjacent tubes so as to create a network of communicating tubes
that isolate at least one tube or a group of non-communicating
tubes, whereby at least one of the communicating tubes is connected
to at least one hot gas intake.
According to the invention, certain cells of the coating are
dedicated exclusively to acoustic treatment and do not comprise any
opening outside of the acoustically resistive layer.
Other characteristics and advantages will emerge from the following
description of the invention, a description that is provided only
by way of example, with regard to the accompanying drawings, in
which:
FIG. 1 is a perspective view of a propulsion unit of an
aircraft,
FIG. 2 is a longitudinal cutaway that illustrates an air intake of
a nacelle according to the invention,
FIG. 3 is a top view of an alveolar structure according to a first
variant of the invention,
FIG. 4 is a top view of an alveolar structure according to another
variant of the invention,
FIG. 5 is an elevation view that illustrates a longitudinal band
that is arranged in a radial plane,
FIG. 6A is an elevation view that illustrates a first transverse
band that is arranged along a first surface that is secant with the
radial planes,
FIG. 6B is a perspective view that illustrates in perspective the
first band that is illustrated in FIG. 6A,
FIG. 7A is an elevation view that illustrates a second transverse
band that is arranged along a second surface that is secant with
the radial planes, whereby said second surface follows the top part
of the rim of a nacelle air intake,
FIG. 7B is a perspective view that illustrates the second band that
is illustrated in FIG. 7A, which can be curved to overlap with the
first bands,
FIG. 8 is a perspective view along a first angle of view
illustrating an alveolar structure according to the invention that
can be adapted to an angular sector of an air intake,
FIG. 9 is a perspective view that illustrates in detail the
connection between a longitudinal band and a transverse band,
FIG. 10 is a perspective view along a second angle of view that
illustrates an alveolar structure according to the invention that
can be adapted to an angular sector of an air intake, and
FIG. 11 is a perspective view that illustrates an air intake in
detail.
This invention is now described applied to an air intake of a
propulsion unit of an aircraft. However, it can be applied to
different leading edges of an aircraft where an acoustic treatment
and a frost treatment are performed, for example the leading edge
of the wings.
Hereinafter, frost is defined both as frost and ice, of all kinds,
all structures and all thicknesses.
In FIG. 1, a propulsion unit 10 of an aircraft that is connected
under the wing by means of a mast 12 is shown. However, this
propulsion unit could be connected to other zones of the
aircraft.
This propulsion unit comprises a nacelle 14 in which a power plant
that drives a fan that is mounted on its shaft 16 is arranged
essentially concentrically. The longitudinal axis of the nacelle is
referenced 18.
The nacelle 14 comprises an inside wall 20 that delimits a tube
with an air intake 22 toward the front.
The top part 24 of the air intake 22 describes an essentially
circular shape that extends in a plane that can be essentially
perpendicular to the longitudinal axis 18, as illustrated in FIG.
2, or not perpendicular, with the top part located just before 12
o'clock. However, other air intake shapes can be considered.
Hereinafter, aerodynamic surface is defined as the shell of the
aircraft that is in contact with the aerodynamic flow.
To limit the impact of pollution, a coating 26 whose purpose is to
absorb a portion of the sound energy, in particular by using the
principle of Helmholtz resonators, is provided in particular at the
aerodynamic surfaces. In a known way, this acoustic coating, also
called an acoustic panel, comprises--from the outside to the
inside--an acoustically resistive layer 28, at least one alveolar
structure 30, and a reflective layer 32.
Layer is defined as one or more layers that may or may not be of
the same type.
The acoustically resistive layer 28 is a porous structure that
plays a dissipative role, partially transforming the acoustic
energy of the sound wave that passes through it into heat.
The reflective layer 32 is impermeable to sound waves and does not
comprise an opening that can affect acoustic treatment.
These different layers are not described in more detail because
they are known to one skilled in the art.
The alveolar structure 30 corresponds to a volume that is delimited
by, on the one hand, a first imaginary surface 34 to which the
reflective layer 32 can be connected, and, on the other hand, a
second imaginary surface 36, to which the acoustically resistive
layer 28 can be connected, as illustrated in FIG. 8.
The distance that separates the first imaginary surface 34 and the
second imaginary surface 36 cannot be constant. Thus, this distance
can be more significant at the rim of the air intake so as to
impart to said structure a greater resistance, in particular to
impacts.
The alveolar structure 30 comprises a number of tubes that empty
out, on the one hand, at the first surface, and, on the other hand,
at the second surface. These tubes are sealed by, on the one hand,
the acoustically resistive porous layer, and, on the other hand,
the reflective layer, so as to form a cell.
Preferably, two adjacent tubes are separated by a side wall.
To further reduce the noise pollution, the air intake 22 comprises
an acoustic coating 26 on at least one portion of the aerodynamic
surface.
According to one embodiment, this acoustic coating 26 extends from
the inside wall 20 of the nacelle up to the top part 24 of the air
intake over the entire periphery of the air intake. Preferably, as
illustrated in FIGS. 2 and 6, the acoustic coating 26 extends
beyond the top part 24 of the air intake and covers a portion of
the outside surface 34 of the nacelle.
To limit the formation of frost or to prevent its accumulation, the
air intake 22 comprises means for treating the frost.
This invention relates more specifically to a frost treatment
process that consists in using the hot air that is taken from the
engine and fed back at the inside wall of the aerodynamic
surface.
According to the invention, the alveolar structure 30 comprises
cut-outs or openings 38 that are made at the side walls of certain
tubes that make it possible to link adjacent tubes so as to create
a network of communicating tubes isolating at least one tube or a
group of non-communicating tubes. In addition, the alveolar
structure comprises at least one intake for a hot gas 40 at the
side of the alveolar structure.
According to one embodiment, the alveolar structure comprises
cut-outs at certain edges of the side walls that can be arranged at
the second imaginary surface 36 that is coated by the acoustically
resistive layer.
Thus, contrary to the prior art, the alveolar structure preserves
non-communicating cells with a single surface that is permeable to
sound waves, the one coated with the acoustically resistive layer.
Thus, the operation of these non-communicating cells is not altered
by the frost treatment, whereby the reflective layer remains
impermeable.
According to a first embodiment illustrated in FIG. 3, the alveolar
structure 30 consists of a honeycomb. Thus, the tubes have a
hexagonal shape and the adjacent tubes are separated by side walls.
According to the invention, the tubes that are arranged along
certain diagonal lines communicate via cut-outs or openings 38.
Preferably, the tubes communicate along first diagonal lines 42
that are oriented in a first direction and along second diagonal
lines 44 that are oriented in a second direction. This
configuration makes it possible to isolate groups 46 of
non-communicating tubes via their side walls. By way of example,
the communicating tubes, illustrated by gray tints in FIG. 3, make
it possible to isolate nine non-communicating tubes.
According to another variant illustrated in FIGS. 4, 5, 6A, 6B, 7A,
7B, and 8 to 11, the alveolar structure 30 comprises, on the one
hand, a number of first bands 48 called longitudinal bands that
correspond to the intersection of the volume with radial planes
incorporating the longitudinal axis 18, and, on the other hand, a
number of second bands 50 called transverse bands that correspond
to the intersection of the volume with surfaces that are secant
with the radial planes. Preferably, at each point of intersection
with the second imaginary surface 36, each transverse band 50 is
approximately perpendicular to the tangent at the second imaginary
surface 36 at the point under consideration.
Preferably, at each point of intersection with the transverse bands
50, each longitudinal band 48 is approximately perpendicular to the
tangent of each transverse band 50 at the point under
consideration.
Secant surface is defined as a plane or a surface that is secant
with the first imaginary surface 34 and with the second imaginary
surface 36.
More generally, the alveolar structure comprises a series of first
bands 48 that are arranged at the secant surfaces, whereby said
first non-secant bands 48 are spaced apart, and at least one second
series of second bands 50 that are arranged at secant surfaces,
whereby said second non-secant bands 50 are spaced apart. The first
bands 48 are secant with the second bands so as to delimit a tube
between, on the one hand, two first adjacent bands, and, on the
other hand, two second adjacent bands.
Thus, tubes with four lateral surfaces are obtained.
Likewise, to simplify the design, the first bands will be arranged
in radial planes that contain the longitudinal axis of the
nacelle.
To obtain a more rigid structure, the second bands will be arranged
so that they are approximately perpendicular to the first bands so
as to obtain tubes with square or rectangular cross-sections. This
solution also makes it possible to simplify the design. However,
other cross-section shapes, for example, diamond-shaped, can be
considered.
At curved zones, the cross-sections of the tubes are tapered. Thus,
they vary between a large cross-section at the second imaginary
surface 36 and a smaller cross-section at the first imaginary
surface 34.
To assemble the bands of the different series that intersect, first
cut-outs 52 are provided at the longitudinal bands 48 that work
with second cut-outs 54 at the transverse bands 50. It is
understood that it is sufficient to increase the number of cut-outs
on each of the bands in the event of a number of series of bands
that is greater than two.
The first and second cut-outs 52 and 54 do not extend from one edge
to the next to facilitate the assembly.
The length of the first cut-outs 52 and that of the second cut-outs
54 are adjusted so that the edges of the longitudinal bands and
transverse bands are arranged at imaginary surfaces 34 and 36.
According to one embodiment, the first cut-outs 52 extend from the
edge of the longitudinal bands arranged at the second imaginary
surface 36. In addition, the second cutouts 54 extend from the edge
of the transverse bands arranged at the first imaginary surface
34.
According to one embodiment, the shape of the alveolar structure 30
that it will have when it is installed at the surface to be treated
is digitized. The longitudinal and transverse bands are then
positioned virtually so as to define the geometries for each of
them. It is possible to make the surface area discrete using the
same method as networking software. Making the surface area
discrete is done by projection of geometries.
Thus, as illustrated in FIG. 5, in the case of an air intake, the
longitudinal bands 48 have a C shape with a first edge 56 that is
able to correspond to the first imaginary surface 34 and a second
edge 58 that can correspond to the second imaginary surface 36.
According to the variants, the distance that separates the edges 56
and 58 can vary from one band to the next or along the profile of
the same band. The longitudinal bands 48 are cut out into
essentially flat plates. This flat cutout simplifies production. To
the extent where the longitudinal bands 48 are arranged in radial
planes, they are not curved during the assembly with the transverse
bands 50.
As illustrated in FIGS. 6A, 6B, 7A and 7B, in the case of an air
intake, the transverse bands 50 have ring shapes with a first edge
60 that can correspond to the first imaginary surface 34 and a
second edge 62 that can correspond to the second imaginary surface
36. The edges 60 and 62 have a radius of curvature that is able to
vary gradually, based on the distance with the top part 24, from a
value R that corresponds approximately to the radius of curvature
of the tube that forms the nacelle for the transverse bands 50, as
illustrated in FIG. 6A, and an infinite radius, whereby the edges
60 and 62 are approximately rectilinear, as illustrated in FIG. 7A,
for the transverse band 50 that is arranged at the top part 24 of
the air intake.
The transverse bands 50 are preferably cut out into essentially
flat plates.
One advantage of the invention resides in the fact that the
transverse and longitudinal bands are cut out flat, which
contributes to simplifying the production and they do not undergo
any shaping operation, which ensures the adjustment of cells on the
reflective layer and the acoustically resistive layer.
The transverse bands, based on their position, are flexible enough
to be able to be optionally curved so as to overlap in the
longitudinal bands. As illustrated in FIG. 6B, the transverse bands
50 that are arranged in zones of the alveolar structure that have a
single radius of curvature, in particular the approximately
cylindrical parts, are arranged in planes once assembled.
The majority of the transverse bands 50 are flexible enough to be
optionally curved along a radius of curvature r that is
perpendicular to the surface of the bands, as illustrated in FIG.
7B, based on their position at the alveolar structure. Thus, the
transverse bands 50 that are removed from the top part 24 are not
curved, which corresponds to an infinite radius of curvature r,
whereby the transverse bands 50 have a radius of curvature r that
gradually decreases based on the distance that separates the
transverse band under consideration of the top part 24 up to a
radius r that is approximately equal to the radius of the top part
for the transverse band 50, illustrated in FIGS. 7A and 7B,
arranged at the top part 24.
According to an important advantage of the invention, the bands are
no longer deformed once assembled or when the reflective or
acoustically resistive layers are installed.
Whereby the thus constituted acoustic coating has shapes suited to
those of the surface to be treated, it is no longer deformed during
its installation at said surface to be treated. Consequently,
contrary to the prior art, the connection between the alveolar
structure and the reflective layer or the acoustically resistive
layer no longer runs the risk of being damaged, and the position of
the walls of the tubes that correspond to the bands is perfectly
known and the side walls remain at the desired positions during the
digitization.
As illustrated in FIG. 9, the longitudinal bands 48 and the
transverse bands 50 are assembled and then connected to one another
by welding, for example a brazing 64, or by gluing. However, other
solutions for ensuring a connection between the bands can be
considered.
According to the variants, the edges of the bands can have more
complex shapes and comprise several radii of curvature so as to
obtain more complex surfaces.
If appropriate, it is possible to vary the spacing between the
bands of the same series.
Thus, the first consecutive cut-outs 52' and 52'' can have a
smaller spacing so as to obtain a slight spacing between the
consecutive transverse bands 50' and 50'' as illustrated in FIG. 8.
Likewise, the second consecutive cut-outs 54' and 54'' can have a
smaller spacing so as to obtain a slight spacing between
consecutive longitudinal bands 48, 48'' as illustrated in FIG.
8.
This arrangement makes it possible to obtain cells with variable
cross-sections.
According to the invention, so as to provide the function of frost
treatment, the bands 48 and 50 can comprise cut-outs 38 to link
certain cells to one another and to obtain a network of tubes. This
solution makes it possible to generate a network of tubes, located
between the consecutive bands 48 and 50 that are brought close
together and are used to channel hot air and to provide the frost
treatment function, as illustrated in FIG. 4.
The non-communicating cells are used for the function of acoustic
treatment.
This configuration makes it possible to make the functions of frost
treatment and acoustic treatment compatible, whereby certain
coating cells, those that do not communicate with one another, are
provided exclusively for acoustic treatment and others, those that
communicate with one another, for frost treatment.
Contrary to the solution that uses a honeycomb alveolar structure,
this arrangement makes it possible to adapt the cross-sections of
cells based on their function. Thus, the cells 66 that are
dedicated to the channeling of hot air for the frost treatment have
small cross-sections, and they are delimited by bands 48, 50 that
are brought close together whereas the cells 68 that are dedicated
to acoustic treatment have larger cross-sections. Thus, as
illustrated in FIG. 10, the surface that is occupied by the cells
66 that are dedicated to the acoustic treatment is reduced at the
second imaginary surface so as not to reduce the area of the
surfaces corresponding to the cells 68 that ensure the acoustic
treatment.
As illustrated in FIG. 11, a cavity or a channel 70 into which at
least one intake of hot gas, in particular hot air that originates
from the power plant, empties out, is provided at at least one
portion of the periphery of the alveolar structure 30 of air 40,
whereby said at least one channel or cavity 70 communicates via
openings or cut-outs 38 with at least one cell 66 that is dedicated
to frost treatment.
According to another advantage that originates from the embodiment
that is illustrated in particular in FIG. 10, whereby the alveolar
structure 30 is not deformed after the bands are assembled, there
is no risk of crushing tubes that are used for the frost treatment
contrary to the honeycomb solution for which the deformation of the
side walls in a random manner during the installation of the
coating could lead to the crushing of certain tubes.
According to another advantage, it is possible to distribute the
de-icing air precisely by adapting the spacing between the bands to
reduce the passage cross-section based on the spot where it is
necessary to de-ice in a more significant manner.
Preferably, the acoustically resistive layer 28 that is provided on
the second imaginary surface can comprise perforations or
microperforations that are provided to link the inside of the cells
of the alveolar structure with the outside. Certain perforations or
microperforations are thus designed for acoustic treatment and
others for frost treatment.
Advantageously, at least the perforations or microperforations that
are provided for the frost treatment are inclined and are not
normal with respect to the outside surface of the acoustically
resistive layer so as to evacuate the hot air in a laminar manner
at the outside surface that is to be treated. This configuration
also makes it possible to reduce the risk of obstructing holes
(perforations or microperforations), in particular by
pollution.
Of course, the invention obviously is not limited to the embodiment
that is shown and described above, but on the contrary it covers
all of the variants thereof.
Thus, this invention is not limited to the leading edge but can be
applied to all of the coatings for acoustic treatment that can
treat frost with a hot gas.
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